EP0052053A1 - Verfahren und Vorrichtung für Flugüberprüfungen des kathodischen Schutzes unterirdischer Rohrleitungen - Google Patents

Verfahren und Vorrichtung für Flugüberprüfungen des kathodischen Schutzes unterirdischer Rohrleitungen Download PDF

Info

Publication number
EP0052053A1
EP0052053A1 EP19810401758 EP81401758A EP0052053A1 EP 0052053 A1 EP0052053 A1 EP 0052053A1 EP 19810401758 EP19810401758 EP 19810401758 EP 81401758 A EP81401758 A EP 81401758A EP 0052053 A1 EP0052053 A1 EP 0052053A1
Authority
EP
European Patent Office
Prior art keywords
pipeline
magnetometer
magnetic field
current
aircraft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19810401758
Other languages
English (en)
French (fr)
Inventor
Michael Edward Stamm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NORTHWEST ENERGY Co
Original Assignee
NORTHWEST ENERGY Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NORTHWEST ENERGY Co filed Critical NORTHWEST ENERGY Co
Publication of EP0052053A1 publication Critical patent/EP0052053A1/de
Ceased legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/15—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat
    • G01V3/165—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat operating with magnetic or electric fields produced or modified by the object or by the detecting device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/02—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with propagation of electric current
    • G01V3/04—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with propagation of electric current using dc

Definitions

  • This cathodic protection of pipelines is achieved by impressing on the pipe a DC current of approximately 50 milliamps per square meter of surface area of the pipe.
  • a DC current of approximately 50 milliamps per square meter of surface area of the pipe.
  • it is commonplace to provide rectifiers along the length of the pipeline, the distances between rectifiers being as little as 300 meters and as much as 80kilcmeters, depending on the soil resistivity, its corrosive or non-corrosive nature, the size of the pipeline, the quality of coating and other factors.
  • the prior art utilizes one of two techniques for "close interval" monitoring of the current in a pipeline.
  • the first method involves the use of one or more people who walk on the pipeline right-of-way, with two or more probes, each . at least 1.2 meter in length.
  • the probes are either like walking sticks or are multi-probes mounted on a wheel.
  • the probes are electrodes, .which are connected to a high impedance potentiometer, which is balanced to measure the current in the pipe as the individuals walk along the pipeline.
  • the probes In order for this technique to function, the probes must pierce the coating of the pipe in order to touch the pipe. This damages the coating, and thereby substantially increases the prospect of corrosion, a self-defeating approach.
  • the typical cost for performing such a monitoring survey at mid-1980 was approximately $250 to $280 per km. In addition, it is obviously a slow and tedious process, requiring many days to monitor a nominal pipeline distance of, say, several hundred kilometers.
  • test leads welded to the pipe when the pipe is installed, with the test leads extending through a protective pipe to the surface.
  • test- leads could be welded to an iron pipe, extending up to the ground, so that the test leads can be connected to a balanced shunt circuit to determine the current flow between the test leads.
  • This technique has many shortcomings. First of all, it is too expensive to have test leads located much closer together than one mile, so it only gives an approximate distance for a problem. The current flows measured are highly dependent on the quality of the welds of the leads to the pipe and the welds deteriorate in time, so that a small change in the weld- pipe interface resistance will produce a substantial inaccuracy in the reading.
  • the lowest level of current which can accurately be measured by the prior art techniques is approximately 800 milliamps, which corresponds to a distance between probes of about 600 meters, so that problems can only be determined within limits of 600 meters. This is obviously not ideal.
  • DC magnetometers have been used to measure the presence of ore deposits or for detecting submarines, for example.
  • United States Patents Numbers 3,490,032, 3,604,660, 3,663,953 and 3,808,519 show various devices using DC magnetometers for the detection of sub-surface metallic deposits. Although somewhat similar in concept to the process and apparatus of this invention, these apparatus would not be satisfactory for commercial use because they would not provide an accurate and economical measurement of the current flowing within sub-surface pipes.
  • the invention is applied to pipelines to which is impressed a DC current which pulsates at 120 Hz, and is used to prevent corrosion.
  • the invention includes an apparatus for the accurate detection of a magnetic field created by the passage of direct current in a ferrous object, such as a pipeline, located below the surface of the earth.
  • the apparatus is mounted for use on an aircraft, such as a helicopter, and includes at least one AC magnetometer, filter means operatively associated with the magnetometer to filter out magnetic fields caused by DC voltages of magnitudes different from the one to be measured, at least one magnetic field sensor operatively associated with the magnetometer, means mounting the sensor exterior to an aircraft, and means to display or record the output of the magnetometer.
  • the invention also includes a process for detecting the existence of DC current and measuring its magnitude in an underground pipeline, by the utilization of an AC magnetometer substantially as described above.
  • the apparatus and process of this invention overcome the numerous shortcomings of the prior art'by providing an airborne apparatus and process capable of measuring accurately the presence, location and magnitude of a DC current in an underground pipeline.
  • the invention prefferably includes three magnetometers, spaced from each other to provide plural readings of the magnetic fields being sensed, to provide a sensing accuracy which can eliminate the effects of, for example, a parallel, proximate pipeline. This is important because pipelines frequently are present in parallel pairs.
  • a radar altimeter in conjunction with the magnetometers to permit measurements of the depth of ground cover above the pipeline being inspected contemporaneous with the measurement of its DC current.
  • the process and apparatus of this invention are able to locate and measure the protective currents in those pipeline segments which are located underwater, which is not possible with prior art techniques.
  • This invention produces two other benefits, because of the relatively precise nature of the information which it generates.
  • First of all by evaluating, from time to time over a period of time, the current flow in a given section of pipeline having a given type of coating, accurate data can be developed from which to evaluate the performance of the coating and thereby to aid in developing superior and more reliable coatings.
  • oil and gas "pirates” who will pirate oil or gas from an underground pipeline without payment.
  • Such an underground connection produces a sharp current drop at the point of connection. This drop can be seen on a read-out of the data developed by this invention and used to assist in detecting and perhaps also discouraging such piracy.
  • Another object of this invention is to provide a magnetometer apparatus capable of accurately and speedily measuring the DC current flowing in each of two proximate, parallel pipelines.
  • Yet another object of this invention is to provide an apparatus and process to measure the ground cover over a pipeline quickly and accurately and to do so contemporaneous with measuring the protective current in the pipeline.
  • a concomitant object of-this invention is to locate under water pipelines and to measure the protective current therein.
  • a helicopter 10 is provided with a suitable mounting device, generally designated by numeral 12, below its body.
  • Mounting device 12 operatively supports three booms, respectively designated 14, 16 and 18.
  • the helicopter 10 is desirably a Bell Jet Ranger II . helicopter, which is desired for its stability and reliability.
  • the helicopter is selected so that it will travel at an elevation which is desirably approximately thirty meters above ground level, at a speed which is desirably about eighty kilometers per hour.
  • a helicopter is preferred to a conventional standard take-off and landing aircraft because the helicopter turns corners better and also flies much better at low speeds and altitudes, such as used in the process of this invention.
  • Platform 12 may be a commercially available Chadwick carrier, which is commonly used for mounting luggage below a helicopter fuselage.
  • the booms, 14, 16 and 18, are preferably made of graphite or other suitable non-ferrous mateial to possess the desirable qualities of strength, rigidity, lightness of weight and non-ferrous characteristics.
  • the booms may be rigidly mounted to carrier 12 or to the undercarriage of the helicopter.
  • each of the booms has mounted at its end a sensor, respectively designated 20, 22 and 24.
  • the booms are located at right-angles to each other, boom 16 being located in line with the longitudinal axis of helicopter 10, and booms 14 and 18 being perpendicular thereto.
  • a sensor At the remote end of each of the three booms is located a sensor, respectively designated 20, 22 and 24, the purpose of which is to sense the magnetic field created by the current in the pipe being measured.
  • Each of the booms is approximately forty meters in length. Although the invention is described as having three booms, which is the minimum number desired in order to provide. for maximum sensitivity and accuracy of the measurement of cathodic currents in underground pipelines, it is within the purview of this invention to have fewer or more than thre& booms. Three or more booms are most necessary if parallel,- proximate pipelines are being surveyed, as is frequently the case, to provide sufficient information to be able to differentiate between the currents in the two individual pipelines. In determining whether or not to use a single sensor or plural sensors, another factor to be taken into consideration is the effect of the wind. If the effect of the wind is not to be significant, and only one pipeline is to be measured (rather than proximate parallel pipelines) one sensor would be satisfactory. However, realistically, it is desirable to have at least two sensors and preferable to have three.
  • the three sensors, 20, 22 and 24, are identical AC magnetometers, commonly known as surge coils.
  • the cores of the magnetometers are formed of mu-metal alloy, of a type which is well-known and is commonly used for magnetic cores.
  • Each core is cylindrical in shape, having a length of 2.5 cm. and a diameter of 1.25 centimeter.
  • Each core is wound with 300,000 turns of size 42 copper wire, in order to produce the desired sensitivity, although it will be appreciated that the precise wire size, core size, number of turns and similar variables can be reasonably varied without departing from the spirit or the scope of this invention.
  • each sensor When sensing the magnetic field being detected, it is desirable to break up the magnetic field vector into x, y and z axis coordinates, so that each sensor produces signals which are broken down into the three components of each magnetic field vector.
  • the purpose of this is to allow adjustments to be made for movement of the aircraft bearing the sensors in the x, y and z directions in order to compensate for the effect of wind. If wind is or may be a factor, the use of the three coordinates is necessary.
  • This three-axis information also facilitates the determination of the influence of magnetic fields other than the one being measured as when there are parallel, proximate pipelines.
  • the current which passes in underground pipes is typically 120 cycle, rectified pulsating DC current.
  • This current creates a 120 cycle magnetic field, which is to be detected by the apparatus and process of this invention.
  • the magnetic field of the earth is approximately 1,000 to 10,000 times larger than the magnetic field which is to. be detected by the process and apparatus of this invention.
  • the AC-magnetometers are particularly suitable for this purpose, because DC-magnetometers are so sensitive that false readings are given because of the effect of other magnetic phenomena around the pipeline being measured.
  • the AC-magnetometer can be adapted for the purposes of this invention by the use of a filter, which is preferably a digital filter, for the purpose of screening out all extraneous signals, so that the AC-magnetometer can be made sensitive only to the particular magnetic field created by the 120 cycle current in the ferrous pipeline being measured. This cannot be done with a DC magnetometer while maintaining the sensitivity requisite to clear, accurate, meaningful readings.
  • a filter which is preferably a digital filter
  • the digital filter can be modified so that the process and apparatus of the invention will measure only the characteristics of the DC current in the pipelines and extraneous signals will be filtered out.
  • an AC-magnetometer is designated by numeral 40, and the magnetometer output is connected to a pre-amplifier 42, for the purpose of amplifying the output signal of the magnetometer and assuring that there is an adequate signal corresponding to any relatively weak signals which are being sensed by the magnetometer.
  • the pre-amplifier 42 is a standard audio pre-amplifier, of a type which is used for military purposes.
  • a suitable, commercially- available pre-amplifier is an RCA CA003 integrated circuit unit.
  • the filter would operate on the output of each magnetometer.
  • The.output signal for each magnetometer after having been amplified, is passed through a digital filter, which is set to filter out all signals other than those corresponding to an electric field produced by a rectified, pulsating DC current of 120 cycles.
  • Suitable digital filters are commercially available, but in the practise of the invention it is often preferred to save money by constructing the digital filter independently.
  • Each filtered signal is then passed through an amplifier 46 to amplify the magnitude of the signal and make it more easy to handle by the microprocessor 50.
  • the output of the amplifier 46 is fed into a analog to digital converter 48, which converts the AC output signal of the amplifier to a digital signal, to facilitate handling by the microprocessor.
  • the microprocessor 50 includes a multiplexer, which is commercially available from DATEL, and the purpose of this is to separate and multiplex each of the nine signals produced by the three magnetometers, 20, 22 and 24.. These signals represent the x, y and z axis coordinates of each of the three magnetometer signals. As discussed below, an altimeter signal, position indicator and clock produce a single output which identifies the particular point in the pipeline at which the magnitude and direction of the current are being measured.
  • the microprocessor 50 is a small computer which is provided with the signals which represent the components of the magnetic field being measured and coordinates them with the time and position signals, so that the microprocessor output will show the magnitude of the magnetic field of the pipeline being measured or the current flow in the pipeline which created the magnetic field plotted against.the coordinate of time or distance.
  • the x-axis coordinate of the output can be distance (meters along the pipeline from a reference point) and the y-axis coordinate can be current in milliamps, for example, to give the current at any point along the pipeline.
  • the resulting output- can be read and the areas noted along the length of the pipeline where current flow is beneath the minimum level necessary to protect the pipe. With the defective pipe segments thus pinpointed, a repair crew can be sent out to dig down to the pipe and allow the defective coating to be repaired.
  • an alarm can be connected to the microprocessor so to provide an instantaneous indication in flight of when the current in the pipeline is below a given reference value, so that prompt action can be taken to resolve the problem.
  • the output of the microprocessor 50 can be stored on magnetic tape or discs or other suitable storage means 52, so that the output can be reviewed and put in manually readable form when the helicopter lands. This could be done in the helicopter, too, but that is usually not necessary.
  • the helicopter is equipped with an altimeter, such as a commercial FMCW radar altimeter which is available from Collins Radio.
  • the altimeter allows the elevation of the helicopter to be determined continuously with respect to the ground'arid with respect to the underlying pipeline so that the one can be subtracted from the other and a determination made of the ground cover between the pipeline and the surface of the ground.
  • the ground cover is usually required by law to be at least ninety centimeters. However, weather conditions, erosion and other circumstances can reduce the amount of ground cover, and it is necessary to determine the cover in order to see if there is any problem.
  • the vertical dotted line 30 in Figure 1 symbolically represents the waveform sent out by the radar altimeter.
  • the two dotted lines 32 and 34 in Figure 1 represent the waveforms sent out by the position indicator, which is a Doppler positioner, for the purpose of measuring the velocity of the aircraft with respect to the ground and locating the aircraft with respect to a reference, such as the beginning of the pipeline or the point at which measurement begins. Since pipelines are normally straight, and the aircraft is traversing a known linear path, the only knowledge which is required to be able to determine the position of the aircraft along the pipeline, once a starting point has been established, is a determination of the velocity of the aircraft at any given point in time. Time is simply measured by a clock which is part of the apparatus. However, other commercially available positioning systems, such as the Omega, Loran or Global Positioning System units, would be appropriate and usable in the apparatus of this invention.
  • the signal from the altimeter, clock and the position indicator are also fed into the microprocessor 50 (the feed-ins are not illustrated), so that the ultimate printout or reading not only provides a signal which is indicative of the current in the pipeline at any given point, but also identifies that point (in time and distance) and identifies the ground cover at that point.
  • the total package of equipment including the sensors, booms, altimeter, Doppler positioner, and the other equipment schematically illustrated in Figure 2 only weighs approximately 130 kilograms in a commercial embodiment of the invention. It will therefore be appreciated that, although the type of equipment and therefore its weight can vary, the weight can reasonably easily be handled by a conventional commercial helicopter or other aircraft.
  • rectifiers are placed at uniform intervals along the pipelines for the purpose of maintaining a relatively constant (although it may vary substantially) current throughout the pipeline.
  • the distances between rectifiers can vary from 300 meters apart to eighty kilometers apart, depending upon the soil resistivity (whether or not it is corrosive), size of the pipeline, quality of coating and other factors.
  • the rectifier produces a current of one amp to one hundred amps, again depending upon the particular conditions of the soil, size of pipeline and quality of coating.
  • the current which was capable of being measured which decreases substantially with distance from the rectifiers, can be measured at the distance most remote from to the nearest rectifiers (i.e.
  • pipelines are generally buried underground, they are required at times to traverse bodies of water, in which case they are typically located below the water surface at a level so as not to interfere with shipping or other aquatic uses in the area.
  • Sub-surface pipelines are capable, because of the way in which they are mounted, of being moved somewhat upstream or downstream as a result of current flow and other similar ambient conditions. It is, therefore, also important in the practice of this invention to be able to locate and determine the condition of currents flowing through pipeline sections which are located under water. The apparatus and process of this invention are able to serve that function.
  • the process and apparatus of this invention allow the pipeline to be located, and the current characteristics in the pipeline to be determined, in the same manner as is the case with those portions- of pipelines which are located underground. This also enables the underwater pipeline to be located by the identification of the.magnetic field it creates which is measured by this invention. This is not at all possible (location of underwater pipe and measurement of protective current therein) with the available prior art techniques.
  • the necessary electrical equipment and the three booms, with sensors mounted on their ends, in the manner illustrated in Figure 1 was mounted on a Bell Jet Ranger II helicopter and flown along an underground pipeline at elevations which varied from fifteen to about thirty meters.
  • 320 kilometers of pipeline were flown in a period of four hours, and the results of the magnetometer, altimeter and Doppler positioner measurements were recorded on magnetic tape.
  • the magnetic tape was then returned to a laboratory site, at which time it was used to produce a graphic printout which illustrated the cathodic current continuously along the pipeline, in addition to representing the depth of ground cover.
  • the process of the invention therefore involves, in broad outline, the following steps:
  • a radar altimeter or similar device can be used in coordination with the magnetometer in order to determine the depth of ground cover at each point along the pipeline being surveyed.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • Remote Sensing (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Electromagnetism (AREA)
  • Geophysics And Detection Of Objects (AREA)
EP19810401758 1980-11-07 1981-10-30 Verfahren und Vorrichtung für Flugüberprüfungen des kathodischen Schutzes unterirdischer Rohrleitungen Ceased EP0052053A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US20494080A 1980-11-07 1980-11-07
US204940 1980-11-07

Publications (1)

Publication Number Publication Date
EP0052053A1 true EP0052053A1 (de) 1982-05-19

Family

ID=22760106

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810401758 Ceased EP0052053A1 (de) 1980-11-07 1981-10-30 Verfahren und Vorrichtung für Flugüberprüfungen des kathodischen Schutzes unterirdischer Rohrleitungen

Country Status (4)

Country Link
EP (1) EP0052053A1 (de)
CA (1) CA1184974A (de)
DE (1) DE52053T1 (de)
MX (1) MX151123A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5610523A (en) * 1991-05-06 1997-03-11 Elliot; Peter J. Method and apparatus of interrogating a volume of material beneath the ground including an airborne vehicle with a detector being synchronized with a generator in a ground loop
US5614908A (en) * 1995-04-14 1997-03-25 Phelan; Joseph P. Helicopter system with rotor blade antennas for landing assistance and for detection of electro-magnetic anomalies
US6483309B1 (en) * 2000-12-11 2002-11-19 The United States Of America As Represented By The Secretary Of The Navy Power frequency magnetic field (PF-MF) detection systems and operating methods therefor
CN104406902A (zh) * 2014-11-19 2015-03-11 中国航空工业集团公司沈阳飞机设计研究所 一种飞机结构抗腐蚀防护能力的评价方法
CN106741753A (zh) * 2015-11-23 2017-05-31 中国科学院沈阳自动化研究所 一种自主水下机器人磁力探头伸缩搭载装置
WO2024100059A1 (de) * 2022-11-07 2024-05-16 Rosen Ip Ag Inspektionsvorrichtung zur untersuchung des kathodenschutzes sowie verfahren hierzu

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6229313B1 (en) 1999-05-27 2001-05-08 Scintrex Limited Mapping of pipeline grounding points by airborne or ground magnetic measurements of current flow in the pipeline

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3490032A (en) * 1966-12-08 1970-01-13 Gulf Research Development Co Method and apparatus utilizing a pair of spaced magnetometers for making magnetic surveys
US3808519A (en) * 1972-06-13 1974-04-30 Commissariat Energie Atomique Method and device for determining the depth of a magnetic anomaly
AU490249B2 (en) * 1974-10-16 1976-04-29 Barringer Research Ltd. Method of detecting conductive bodies
US4130791A (en) * 1977-09-08 1978-12-19 Texaco Inc. Automatic pipe depth locator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3490032A (en) * 1966-12-08 1970-01-13 Gulf Research Development Co Method and apparatus utilizing a pair of spaced magnetometers for making magnetic surveys
US3808519A (en) * 1972-06-13 1974-04-30 Commissariat Energie Atomique Method and device for determining the depth of a magnetic anomaly
AU490249B2 (en) * 1974-10-16 1976-04-29 Barringer Research Ltd. Method of detecting conductive bodies
US4130791A (en) * 1977-09-08 1978-12-19 Texaco Inc. Automatic pipe depth locator

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5610523A (en) * 1991-05-06 1997-03-11 Elliot; Peter J. Method and apparatus of interrogating a volume of material beneath the ground including an airborne vehicle with a detector being synchronized with a generator in a ground loop
US5614908A (en) * 1995-04-14 1997-03-25 Phelan; Joseph P. Helicopter system with rotor blade antennas for landing assistance and for detection of electro-magnetic anomalies
US6483309B1 (en) * 2000-12-11 2002-11-19 The United States Of America As Represented By The Secretary Of The Navy Power frequency magnetic field (PF-MF) detection systems and operating methods therefor
CN104406902A (zh) * 2014-11-19 2015-03-11 中国航空工业集团公司沈阳飞机设计研究所 一种飞机结构抗腐蚀防护能力的评价方法
CN106741753A (zh) * 2015-11-23 2017-05-31 中国科学院沈阳自动化研究所 一种自主水下机器人磁力探头伸缩搭载装置
CN106741753B (zh) * 2015-11-23 2018-07-31 中国科学院沈阳自动化研究所 一种自主水下机器人磁力探头伸缩搭载装置
WO2024100059A1 (de) * 2022-11-07 2024-05-16 Rosen Ip Ag Inspektionsvorrichtung zur untersuchung des kathodenschutzes sowie verfahren hierzu

Also Published As

Publication number Publication date
CA1184974A (en) 1985-04-02
DE52053T1 (de) 1983-01-05
MX151123A (es) 1984-10-03

Similar Documents

Publication Publication Date Title
US5148110A (en) Method and apparatus for passively detecting the depth and location of a spatial or temporal anomaly by monitoring a time varying signal emanating from the earths surface
EP0825456B1 (de) Konditionsbestimmung von einem begrabenen Objekt
US6965320B1 (en) Cathodic test lead and pig monitoring system
US4427943A (en) Apparatus and method for locating and tracking magnetic objects or sources
US4418574A (en) Magnetic method and apparatus for measuring wall thickness
RU88453U1 (ru) Приборный комплекс для бесконтактной диагностики технического состояния подземных трубопроводов м-1
US4430613A (en) Pipeline inspection and maintenance method including moving a magnetic field responsive device along the route of the pipeline
CA2234202C (en) Method and apparatus for detecting, locating and resolving buried pipelines, cased wells and other ferrous objects
CA1178706A (en) Method of detecting cracks in constructions
EP0052053A1 (de) Verfahren und Vorrichtung für Flugüberprüfungen des kathodischen Schutzes unterirdischer Rohrleitungen
CN207440306U (zh) 一种深埋废弃井探测装置
CN209264625U (zh) 一种基于弱磁检测技术的埋地金属管道非开挖检测装置
JP2939334B2 (ja) 可聴周波以下の低周波磁気測定装置
US4365191A (en) Method and apparatus for electrical surveys of offshore metal structures with correction for distance
US3091733A (en) Apparatus for detecting flaws in elongated magnetic structures
CN110794464B (zh) 一种去除时间域航空电磁数据背景场的方法
CA1161115A (en) Pipeline inspection and maintenance method
US3116452A (en) Eddy current type pipeline flaw testing and flaw location marking device
Frischknecht et al. Location of abandoned wells by magnetic surveys; acquisition and interpretation of aeromagnetic data for five test areas
Barrow et al. Collection and analysis of multi-sensor ordnance signatures with MTADS
US6937190B1 (en) Electromagnetic impulse survey apparatus and method
EP3842796A1 (de) Verfahren zur berührungslosen detektion des vorhandenseins, der position und des gefährdungsgrades von spannungskonzentratoren von mechanischen spannungen in metall von ferromagnetischen konstruktionen
DE2530589A1 (de) Verfahren und anordnung zur ueberwachung von rohrleitungen und dergleichen
JP2958071B2 (ja) 地中埋設管の電気防食効果評価法
McConnell et al. Enhanced 3D seismic surveys using a new airborne pipeline mapping system

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

TCNL Nl: translation of patent claims filed
ITCL It: translation for ep claims filed

Representative=s name: JACOBACCI CASETTA & PERANI S.P.A.

DET De: translation of patent claims
17P Request for examination filed

Effective date: 19821110

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: NORTHWEST ENERGY COMPANY

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: NORTHWEST ENERGY COMPANY

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19860213

RIN1 Information on inventor provided before grant (corrected)

Inventor name: STAMM, MICHAEL EDWARD